Ming Saltpeter Refining for Gunpowder

Timeline

1. 1421–1422Beijing · BeijingAfter the Yongle Emperor moved the capital to Beijing, equipping cannons in the capital and along the Nine Borders sharply increased gunpowder demand; the Ministry of Works was ordered to rush-transport saltpeter from producing areas such as Shanxi, Shaanxi, and Fujian, setting up refining and purification points in Beijing and at postal relay stations along the route.
2. c. 1423–1427Taiyuan · ShanxiSaltpeter areas in Shanxi refined saltpeter through leaching of saltpeter earth, brine evaporation, and recrystallization; the government set up bureaus to supervise production and supply the capital garrisons and frontier towns, with some procured by merchant guilds and then refined by the government.
3. 1428–1430Nanjing · NanjingDuring the Xuande era, the Armaments Bureau formulated gunpowder according to ratios of saltpeter, sulfur, and charcoal, tested the purity of saltpeter on intake, ensured gunpowder reserves for the Shenjiying's cannons and Nine Borders garrisons, and established a regular inventory system.